The present invention relates to an SiC single crystal suitable for semiconductor electronic components and a growth method thereof, and more particularly to a 4H poly type SiC single crystal and a growth method thereof.
Current research on a compound semiconductor comprised of such light elements as silicon carbide (SiC) or gallium nitride (GaN) is active. Such a compound semiconductor which is comprised of light elements has a feature where the bonding energy is strong, and as a result the band gap of energy, dielectric breakdown electric field and thermal conductivity are high. SiC in particular is attracting attention as a material for high efficiency high withstand voltage power devices, high frequency power devices, high temperature operation devices or blue to purple light emitting devices, because of this wide band gap feature. However, because of its strong bonding energy, an SiC compound does not melt in atmospheric temperature, and has difficulty in growing bulk crystals by recrystallizing the melt which is performed with other semiconductors, including silicon (Si).
A known method of growing a bulk SiC single crystal is the so called improved Raleigh method described in Japanese Patent Publication No. S59-48792 and Japanese Patent Laid-Open No. H2-30699. In this improved Raleigh method, a seed crystal comprised of SiC single crystals is set in a crucible made of graphite, material SiC powder is sublimated in a lower pressure atmosphere, and a target scale SiC single crystal is recrystallized on the seed crystal.
In a so called sublimation method, including this improved Raleigh method, mainly an SiC single crystal substrate where the {0001} plane is exposed is used as the seed crystal. However, if an SiC single crystal is grown using an SiC single crystal substrate where the plane orientation is {0001}, a defect called a micro-pipe, which extends in the  less than 0001 greater than axis direction, reaches the surface of the single crystal, so in some cases a leak current is generated when a device is fabricated using the SiC single crystal.
A known technology to solve the problem related to a micro-pipe is a method of growing an SiC single crystal described in Patent Publication No. 2804860, for example. In this method, an SiC single crystal, in which the crystal plane which is shifted through an angle xcex1 in a 60xc2x0-120xc2x0 range from the {0001} plane, is used as a seed crystal, and preferably an SiC single crystal, in which a {1-100} plane or {11-20} plane is exposed, is used. If such a seed crystal is used, the micro-pipe reaching the surface of the single crystal can be decreased.
The method of growing an SiC single crystal described in Patent Publication No. 2804860 has the following problem. As the inventors of the invention described in Physical Status Solids (b) (No. 202, pp. 163-175, 1997), when an SiC single crystal where the {1-100} plane or {11-20} plane is exposed is used as a seed crystal, crystal polymorphy can be suppressed, and a micro-pipe reaching the surface can be suppressed, but a high density stacking fault is exposed on the surface of the SiC single crystal. This stacking fault spreads on the plane when the crystal is grown, and if a device is fabricated using such an SiC single crystal where a stacking fault is exposed on the surface, a leak current may be generated, just like the case of using an SiC single crystal where a micro-pipe exposed on the surface is used.
With the foregoing in view, it is an object of the present invention to provide an SiC single crystal where a micro-pipe and stacking fault exposed on the surface is decreased, and a growth method thereof.
The present invention is a method of growing a 4H poly type SiC single crystal, characterized in that a 4H poly type SiC single crystal is grown on a seed crystal comprised of an SiC single crystal where a {03-38} plane or a plane which is inclined at off angle xcex1 within about 10xc2x0 from the {03-38} plane is exposed. In the method of growing an SiC single crystal according to the present invention, if a seed crystal where the {03-38} plane is exposed is used, for example, the exposed plane of the seed crystal has about a 35xc2x0 inclination with respect to the  less than 0001 greater than  orientation where micro-pipes extend. Therefore, if a 4H poly type SiC single crystal is grown on the seed crystal, micro-pipes can reach a side face of the SiC single crystal and the state for micro-pipes to reach the surface can be suppressed. Also the exposed plane of the seed crystal ({03-38} plane) has about a 55xc2x0 inclination with respect to the plane perpendicular to the  less than 0001 greater than  orientation where stacking faults spread, so if a 4H poly type SiC single crystal is grown on such a seed crystal, stacking faults can reach a side face of the SiC single crystal and the state for stacking faults to reach the surface can be suppressed. The exposed plane of the seed crystal may be a plane where off angle xcex1 within about 10xc2x0 is inclined from the {03-38} plane, instead of the {03-38} plane, to suppress the state for micro-pipes and stacking faults to reach the surface of the grown SiC single crystal.
Off angle xcex1 is preferably 5xc2x0. And off angle xcex1 is even more preferred to be within 3xc2x0. In other words, as the surface of the seed crystal becomes closer to the {03-38} plane, the more certain of micro-pipes and stacking faults of reaching the surface can be suppressed.
The SiC single crystal may be grown on the seed crystal by a chemical vapor deposition method.
Another method of growing an SiC single crystal according to the present invention is a method of growing an SiC single crystal for recrystallizing a 4H poly type SiC single crystal on a seed crystal placed in a crucible by sublimating SiC material powder in a crucible made of graphite, characterized in that an SiC single crystal, where a {03-38} plane or a plane which is inclined at off angle xcex1 within about 10xc2x0 from the {03-38} plane is exposed, is used as said seed crystal.
According to such a method of growing an SiC single crystal, if an exposed plane of the seed crystal to be placed in the crucible made of graphite is the {03-38} plane, for example, the exposed plane of the seed crystal has about a 35xc2x0 inclination with respect to the  less than 0001 greater than  orientation to which micro-pipes extend. So if a 4H poly type SiC single crystal is grown on such a seed crystal by sublimating SiC material powder, micro-pipes reach a side face of the SiC single crystal and the state for micro-pipes to reach the surface can be suppressed. Also the exposed plane of the seed crystal ({03-38}) plane has about a 55xc2x0 inclination with respect to the plane perpendicular to the  less than 0001 greater than  orientation where the stacking faults spread, so if a 4H poly type SiC single crystal is grown on such a seed crystal, the stacking faults can reach the side face of the SiC single crystal and the state for stacking faults to reach the surface can be suppressed. The exposed plane of the seed crystal may be a plane where off angle xcex1 within about 10xc2x0 is inclined from the {03-38} plane, instead of the {03-38} plane, to suppress the state for micro-pipes and stacking faults to reach the surface of the grown SiC single crystal.